I've often heard this debate between the two schools of philosophy, pen vs. CAD. On the one hand, designing in CAD allows you to know that what you are creating will be able to make it to production with minimal changes due to the knowledge of your form's proportions vs. what lies underneath. On the other hand, designing in pen first, allows you the freedom of creating a design intent which will no doubt have to modified later on down the road and change significantly.
I was wondering what everyone's thoughts are on this and why they prefer one over the other.

I 100% disagree with your statement.
Just because something is drawn in CAD does not mean that it can be manufactured. And just the opposite can be accomplished with a pen. It more lies in the person who is creating the part or form. I have worked with plenty of people who send me a CAD drawing, and there is no way it was able to be manufactured with "minimal changes" and I have provided and received hand drawings that were much more informative.
Pen and paper allows for much more creativity in my opinion. There were plenty of times sketching that ideas came about from sketches being seen in the completely wrong perspective/intended form or use - that brought on new ideas and directions that would have never came about from a CAD program.

Working in CAD is not going to get you relevant, usable and desirable products, it's just going to get you something you can send to manufacturing faster. This used to be a good thing when there was very little competition, people weren't as design-savvy, and very few people could use CAD. (I remember when my Alias skills alone made me a hot commodity.)

Today designers need to step away from CAD and return their focus to designing for people. This is the only way to stay relevant in a rapidly commoditizing world.

Pen, paper, PCs, Mac, Rhino, Solidworks - THEY ARE ALL TOOLS. Get over it people!

I can stand the sketch zealots out there (same goes for 3D zealots). Design is a problem solving process - that is all that matters and is what your primary focus should be. If you get all tied up in the details of what tools to use, you're missing the point...

If CAD fits in with your process, fine. If sketching is what floats your boat. fine. Just make sure you're solving a problem someone will care about when you're done.

Overall I agree with NYdesignguy... "The ends justify the means" kind of thing... and that holds true for hiring a seasoned designer at the senior level who can show projects in production and can work pretty autonomously within a group. Of course showing sketches tends to show how you owned the process more in my personal book.

When looking at Junior designers right out of school, with no production work to show, I need to see process. Especially since they will work more hands on with the team, and be mentored and guided through the process for their first few years. I need to see they can respond to feedback, generate lots of possible solutions, take 5 and run with them.... sketches do that best.

So in conclusion: Sketching is a must, 2d CAd, pretty essential for communication the next level of detail, 3d CAD is a plus all other things being =

BUT, I'd take a great designer who is an OK sketcher/2d renderer over a poor designer who can render a turd chrome.